(1) Field of Invention
Profilers for indicating and recording the profiles of surfaces of articles.
(2) Description of Prior Art
Heretofore, profilers of the rocking arm type have been provided for tracing surface profiles of articles and for indicating and recording the profiles traced. An example of such a profiler of the single rocking arm type is disclosed in United States Letters Pat. Nos. 3,319,340 and 3,319,341, both issued May 16, 1967, and each entitled "Profile Indicator and Recorder."
A multi-arm type of profiler, by which opposite faces of an article can be traced concurrently is disclosed in U.S. Pat. No. 3,370,355, issued Feb. 27, 1968, and entitled "Profiler."
With profilers of the above patents, for a given size, a high degree of accuracy is obtained, but only if the divergence of the profile from a given mean or median plane is within relatively moderate limits. This is because the rocking arm of each of these profiles is of constant length and hence the article engaging edge of the stylus follows an arcuate path of constant radius about the rocking axis. Accordingly, assuming a tangent to the arcuate path, with the point of tangency at the tracing edge of the stylus in the starting position of the arm, the arcuate path of the stylus edge recedes from the lineal tangential path at a progressively increasing rate the farther the stylus edge travels from the point of tangency or starting position. This affects the degree of accuracy that can be obtained so that, for a given required degree, a given size of profiler is limited to use only for articles of which the profile variations from a given mean or median do not require the stylus to swing through too large an arc.